Three brothers in Minnesota are betting that robots could compete with machines on the farm, too: the huge, and often inefficient, fertilizer applicators made by John Deere and the like. The brothers' Rowbot, in comparison, is so small it can move between rows of crops and fertilize plants one at a time.

"We joked about it being the Roomba of the cornfield," says one of the brothers, Kent Cavender-Bares, referring to the autonomous vacuum cleaner.

The motivation for creating a fertilizer robot is simple: Many farmers overuse fertilizer, and that's costly and bad for the environment. But farmers don't have many tools to help them cut back.

When crops require more nutrients, huge fertilizer applicators, weighing as much as 10 tons with another few tons of fertilizer on board, spray the cornfield at the height of growing season. But much of that fertilizer evaporates or washes away into groundwater or surface runoff because it never reaches the plants' roots.

The Rowbot, which is 2-feet wide and 7-feet long, is designed to apply nitrogen fertilizer with a lot more precision. Inside it are real-time sensors that are studying the plants and making find-tuned adjustments to how much fertilizer is applied to each plant, says Cavender-Bares.

The hope is that the Rowbot would in the long run save farmers money on fertilizer, he says, but it could also prevent the kind of pollution of waterways that's rampant in the Midwest.

So far the Bares brothers have demonstrated Rowbot in Pennsylvania, Illinois, Iowa and Minnesota. Dave Boehnke owns a farm in Iowa and he's one of people who've tested the Rowbot on his property. He says he's not sure if it'll prevent pollution, but the little guy could help potentially solve another a big problem for him.

"There's always a shortage of manpower," he tells The Salt, "So this would be able to spread out our workload getting a key nutrient on [the crops]."

And the smaller machines like the Rowbot, he says, have another added bonus: They're less likely to compact the soil.

"The bigger the machines get, the heavier the machines get," he says. "Soil's really not designed to be smashed with a several ton machine." And those big machines can damage crops, too.

But not everyone's so sure the Rowbot's method of fertilizing in the middle of the growing season is the best way to get the most crops per acre.

"There are pros and cons to every method or timing of application," says Fabián Fernández, a nutrient management specialist at the University of Minnesota. "In some of the research that we have done recently, we've seen that applying nitrogen pre-planting actually produces better yields than during the growing season."

The brothers say they're going to keep testing the Rowbot on corn, and once they've nailed it down, they'll move on to other crops like soybean.

And when it does roll out, it'll be a service — likely in the form of a fleet of 20 Rowbots roving all over a field. The brothers say it should cost around the same as other custom fertilizer application systems. Think of it as a high-tech lawn service for fields.